1. Field of the Invention
The present invention relates to a printing system, a sheet processing method in the printing system, and a storage medium.
2. Description of the Related Art
A conventional printing apparatus includes a plurality of output trays which can stack printed sheets. Japanese Patent Application Publication No. 2004-310746 discusses a printing apparatus like this. The conventional printing apparatus stacks printed sheets onto one output tray and when the amount of sheets stacked on the output tray has reached a predetermined amount, changes the output tray and continues stacking of sheets by using another output tray. The printing apparatus controls a paper discharge tray, while stacking the sheets discharged from a fixed sheet discharge port, to descend until the top sheet of the stacked sheets comes to the same vertical position of the sheet discharge port.
The finisher apparatus like this may not always be able to fully utilize the maximum stacking amount of a tray according to the size of the sheet to be stacked, the configuration of the output mechanism, and the order of output trays to be used. For example, when sheets are output to a finisher apparatus including movable output trays, in order to fully use the maximum stacking amount of a lower output tray, it is desired to output the sheets starting from an upper output tray.
This is because in outputting sheets onto the upper output tray, it is required to control the upper output tray to descend before the sheets are output thereon. To paraphrase this, it is required to secure a sufficient space (i.e., sufficiently low position) for descending the upper output tray.
In other words, if a large amount of sheets has been stacked onto the lower output tray, the sufficiently low descending position cannot be available for the upper output tray. Thus, the sheets stacked on the lower output tray prevents the upper output tray from going down to the lower position. Accordingly, sheets cannot be stacked on the upper output tray. As a result, sheets cannot be output to the upper output tray by the maximum stacking amount thereof.